(JPL News 3 may 2000)

Fiery volcanoes on Jupiter's moon Io are the main source of dust streams that flow from the Jupiter system into the rest of the solar system, according to new findings from NASA's Galileo spacecraft.

The scientists of the Max Planck Institute of Nuclear Physics in Heidelberg, Germany, analyzed the frequency of dust impacts on Galileo's dust detector subsystem. They found peaks that coincided with the periods of Io's orbit (approximately 42 hours) and of Jupiter's rotation (approximately 10 hours). Furthermore, the study of several years of Galileo data showed that the motion of the dust stream particles is strongly influenced by Jupiter's magnetic field, with a unique signature that could exist only if Io were the main contributor to the dust streams.

"Now, for the first time we have direct evidence that Io is the dominant source of the Jovian dust streams," said the lead author of a paper on the findings that appears in the May 4 issue of the journal Nature.

The Jovian dust streams are intense bursts of submicron- sized particles (as small as particles of smoke) that originate in Jupiter's system and flow out about 290 million kilometers (180 million miles), or twice the distance between Earth and the Sun. In this respect, scientists admit that the escape of dust from the Jovian system was a total surprise.

Early in the history of our solar system, before and during the formation of the planets, small dust grains were much more abundant. These charged grains were influenced by magnetic fields from the early Sun, much as the dust on Io is affected by Jupiter's magnetic field today. Studies of the behavior of these dust grains should therefore provide insight into processes that led to the formation of the moons and planets in our solar system. However, the Jovian dust streams, with their Io source, are minor when compared to the huge amounts of dust created in the solar system by comet activity and asteroid collisions. Nonetheless, they add to the variety of dust sources in the solar system. Furtermore, the Jovian dust streams travel so fast that some particles can actually leave the solar system to join the local interstellar medium -- the gas and dust that fill the space between stars.

Taken from :

Yves, Cons. Gen.

May 2000

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